In sawmill, woodworking, or other related industries, sawdust is a natural byproduct that must be dealt with on a regular basis. Sawdust is typically vacuumed out and sent to a dust collector, where it is stored until it can be hauled away. Once the level of sawdust reaches a threshold, it is emptied, typically into a trailer or other mobile storage device. Because sawdust is relatively lightweight and would easily blow out when the trailer is transported, an open top trailer is undesirable. Additionally, in order to load an open top trailer, the dust collector must be raised off of the ground far enough to allow the trailer to drive underneath, creating additional expense and difficulty in servicing. Trailers in the art are enclosed with rear doors that have two holes cut through them. One hole receives the sawdust and the other is for return air that is displaced from the trailer as the sawdust is loaded. Currently, no system exists that controls the dispensing of sawdust, and the process must be manually monitored to prevent the trailer from becoming overfilled, thereby overwhelming the feeding system. The user relies on a visual observation of the dust that is present in the return line or physically stopping the system to observe directly the amount of dust in the trailer. Relying on watching dust presence in the return line is subjective and subject to error based on environmental conditions and buildup in a transparent portion of the return line. When the process is not watched, an inadvertent user could not stop the process in time, overfilling the trailer and filling all of the tubing with sawdust, creating a downtime and possible equipment damage. Disassembling and clearing out the system after it is packed with dust is time consuming and difficult, idling production and adding unnecessary expense. Further, stopping and starting the process for periodic inspection is time consuming, wasteful, and creates premature wear and tear on the equipment. An improved system is needed.